1. Field of the Invention
The present invention relates to a fluorescent lamp having electrodes at both ends of a tubular glass bulb, and a backlight unit and a liquid crystal display device including the fluorescent lamp as a light source. The present invention in particular relates to techniques for improvement in in-dark starting characteristic.
2. Related Art
Due to recent increases in size of liquid crystal display screens, the demand for backlight units for large-screen use is on the increase. Fluorescent lamps, such as external electrode fluorescent lamps having electrodes outside a glass bulb and cold cathode fluorescent lamps having electrodes inside a glass bulb, have been developed for use in such backlight units.
These fluorescent lamps, however, have the following problem. In darkness, it takes time to light up a fluorescent lamp, that is, the fluorescent lamp cannot be started immediately when a starting voltage is applied. To improve this in-dark starting characteristic, a technique of applying an electron emissive material having a high secondary-emission coefficient, e.g. a cesium compound, to an inner surface of a glass bulb at both ends has been proposed. According to this technique, secondary electrons emitted from the cesium compound coating facilitate a discharge when starting the lamp. Thus, the in-dark starting characteristic can be improved (e.g. Japanese Patent Application Publication No. 2001-15065).
However, though the in-dark starting characteristic can certainly be improved, this technique requires a troublesome operation of applying the cesium compound to the inner surface of the glass bulb.